The actress, who is starring in Netflix’s Rebecca adaptation next month, said her advice to her younger self would be to spend more time with her female friends.
She told Harper’s Bazaar UK: “Don’t be obsessed by boys! Hang out with your girl mates. And don’t take everything so seriously – be kind to yourself.”
And James, 31, said she still “feels like a child” despite being in her thirties.
She said: “Lots of girlfriends said to me, ‘Oh, you feel so much relief in your thirties, you know who you are.’ I thought I was there, but then realised I’m actually not.
“I think I’ll probably always be quite a ‘searching’ person… I can’t picture getting to a point where I’ll feel like, ‘Oh, I’ve grown.’ I still feel like a child.”
James, whose film roles include Mamma Mia! Here We Go Again and Yesterday, will play newlywed Mrs de Winter in Rebecca, opposite US actor Armie Hammer.
James said Daphne du Maurier’s 1938 gothic novel, which forms the basis for the film, had a deep impact on her when she read it for the first time.
She added: “I took the role partly because this person’s journey is so profound, and I love that she sides with a murderer – I mean, that’s screwed up. I just thought: I want to get inside that woman’s head.”
The November issue of Harper’s Bazaar is on sale from October 1.
